Normalized A-105 or 316L?

[jalvarez]

We are doing a modification in a line carrying anhidrous Hydrogen Chloride. The original materials are ASTM A-333 Gr 6 for piping and A-350 LF2 or A-420 WPL6 for accesories. We are installing a low point in a Ø 6" line, and we need to install now a 6" blind flange there.
Operating conditions are 12 barg and -26°C (minus 26).
What could be better to install for the blind from the following alternatives:
- An A-105 blind flange, normalized at 900°C for two hours, cooled down in still air, or
- Same flange, but in ASTM A182 F 316L.
I'm asking this because I don't know if the original installation of killed steel is due to something related with corrosion (as said before, the product is anhidrous hydrogen chloride), and there exist a preference in the selection of the material, or it's simply a cost issue.
Thanks for any advice and regards to all.

 

[metengr]

I would use SA-105 material for the blind flange, with a normalized and tempered heat treatment.

 

[SnTMan]

jalvarez, you can probably finesse the MDMT, but I'm curious, why not just use SA-350-LF2?

Regards,

Mike

 

[jalvarez]

SnTMan
We are using A-350 LF2 in all the job, but we need to stop this 6" line in a point. We only have at hand the two mentioned alternatives; to find a blind Ø6" #300 (or a cap) in LF2 is not so easy here.
I'm curious -and surprised- now. What are the reasons to prefer the normalized A-105 over the SS? Stress corrosion probabilities?
Thanks & regards

 

[metengr]

Dissimilar materials in service.

 

[jalvarez]

Taking into account metengr comment, if I have a blind joint, I'll use the SS (but I haven't).
We are using monel graphite joints.

 

[metengr]

Why would you need to use SS, if the remainder of your delivery system is fabricated out of SA 350 LF2 and SA 333 material? To me, I like to avoid introducing dissimilar materials as much as possible. Based on your MDMT requirements, the SA 105 is suitable material for a blind flange application.